Thanks. I already tested the old and new solenoids using that procedure and they are fine.
I am not the greatest at reading elec schematics, but I don't see any other components to check besides the solenoid, key switch, and fuse.
Edit: I somehow missed wolf man’s last two posts. Perhaps I’m just saying the same thing with different words…
I had the exact same problem/symptom with my BX 2200, which is the same tractor as your BX 22.
In my case, it was the run coil in the solenoid that was open. A new solenoid fixed it. In your case it sounds like you’re not getting voltage to the run coil of the solenoid. I don’t recall if there’s a fuse in there but a broken wire would cause the same issue.
What you need to do is verify that the wire going into the run coil on the solenoid is getting voltage when the key is turned to the on position. There is no relay or timer or involved as far as I remember.
Verify that you are getting voltage on the wire that goes into the solenoid to the run coil and report back. You definitely are getting voltage to the start coil in the solenoid because the engine is starting, and only quitting when you release the key.
There is always a chance that your tractor was produced at the end of the production run, and it could share the electrics of the next model in the series. If so, then it would be different than my tractor or the earlier BX 22 tractors. I know this happens sometimes but I’m not sure how frequently or common it is to have different wiring at the end of a production run.